Stirring effect in hydrothermal synthesis of nano C-LiFePO4

• LiFePO4 cathode depends strongly on the frequency of rotation of the impeller.
• Dependence is attributable to the difference in the agglomeration phenomena in secondary particles.
• The presence of secondary particles of size ≈10 μm is beneficial.

C-LiFePO4 positive electrode materials were prepared by hydrothermal synthesis in which the solution was stirred with a rotation frequency varying from 50 to 1150 revolutions per minute (rpm), before carbon coating. The different synthesized cathode materials are discussed and compared in terms of structural, surface-morphological and electrochemical properties. The best C-LiFePO4 electrodes have been obtained using rotation frequencies in the range 280–360 rpm, in which case the capacity retention reaches ∼137 mAh g−1 at coulombic efficiency >99% at C/12, against 106 mAh g−1 in the absence of agitation. Better cycling stability at high current rates (1C) were also obtained. The improved performance of the C-LiFePO4 material obtained by controlled rotating agitation-hydrothermal solution synthesis is attributed to the production of less aggregated particles with high surface area and smaller concentrations of impurities. The controlled rotating agitation of the solution during the synthesis provides a scalable and eco-friendly way of producing better performing electrode particles for use in Li-ion batteries.

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